Putting some bearings on the non-motor side of your lead screws couldn't hurt.
Something like this.
https://www.amazon.com/gp/product/B07RP69XXR/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Your going to be hard pressed to find a drill that big, and a spade bit is probably a bad idea.
Maybe if you know someone else with a router you could bring out the diameter for the holes.